Читать книгу On Naval Timber and Arboriculture - Patrick Matthew - Страница 9

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Oak appears to be the most prevalent tree about the middle of the north temperate zone, growing, naturally, upon almost every soil, excepting some of the sterile sandy hats. With the exception of the pines, it is by far the most useful kind of tree, almost balancing the accommodating figure of stem, and manageable quality of the pine timber, by its greater strength and durability, and excelling the pines in value of bark. It is not easy to determine whether there be distinct British species in the genus Quercus; but, at least, there are several breeds, or families, or grouped resemblances, which, though the individuals may slightly vary, and though a gradation, or connection, may be traced among these families themselves, yet possess general character sufficiently marked to support names. Botanists, who are so prompt and so well prepared with their classes, {32} orders, genera, species, varieties, long before they acquire much knowledge of what they are so ready to classify, or be able to distinguish between species and variety, or know if species and variety be really distinct, divide the oak of this country into two species, Quercus Robur and Q. sessiliflora, the former with long fruit-stalks, and hard, strong, durable timber, the late leafing old kind once so prevalent in the island: the latter an earlier leafing, faster growing kind, timber inferior, leaves petiolate, fruit sessile, not common, but supposed native. We consider there is no foundation for this specific distinction; we have met with oaks with various lengths of fruit-stalks: Besides, short and long fruit-stalks is a very common difference among seedling varieties. The families or breeds which we have observed in the indigenous oak resemble what are found among almost every kind of vegetable, and graduate into each other—those farthest removed in appearance, no doubt having power to commix by the pollen. The most remarkable distinction we have observed is in the colour of the bark, whether inclining to white or black. The variety or breed with grey white bark, often very smooth and shining, and sometimes beautifully clouded with green, has also a different form of leaf and figure of top from those with {33} blackish bark, and we have no doubt will also afford a different quality of timber. Those with blackish dingy bark vary considerably from each other, some being of very luxuriant growth and heavy foliage, with thick fleshy bark, affording much tannin; others, though in favourable situation, of stunted growth, thin dry bark, and delicate constitution, often being nipped in the twigs by the frost: some having a round easy figure of top, even with pendulous branching, others extremely stiff and angular in the branching; some with the most elegant foliage, deeply sinuated and finely waved, others with the clumsiest, most misshapen foliage, almost as if opposite principles had presided at their forming. We have observed the earlier kinds, with the dark bark, to have generally the easiest figure of top; the angular branching and stiffness of figure of top being greatest in those sooty-barked late kinds, most disposed to take two growths in the season, the spring and autumnal, which, from the proneness of these kinds to be affected in the terminal bud by monstrosities, and sometimes also to be nipped in the point of the unripened autumn shoot by the frost, are generally thrown out in different directions, the tree, from these causes, growing awkwardly and irregularly, and by fits and starts.

Besides the indigenous Quercus Robur, we have {34} a number of kinds, termed distinct species, growing in Britain, of foreign derivation—the Turkish oak, Quercus Cerris; the Lucombe oak, Q. sempervirens; the scarlet-leaved American, Q. coccinea; the evergreen, Q. Ilex, and several others. The Turkish and Lucombe resemble each other, but the latter generally continues green till the spring, when the old leaves wither, a little before the young appear: Botanists make them varieties. We consider the Turkish oak the most valuable and elegant of these foreign kinds. The leaves are generally very long and slender, deeply and widely sinuated, and the teeth or salient angles sometimes undulated, having a curled appearance; yet there are some individuals with broad, short, flat leaves, not differing in figure from those of the common oak, but the tree in other respects not different from the Turkish, being easily distinguished from the common oak by the reddish hairy appearance of the developing shoot, the scales of the bud having a hair-like extension, visible in each leaf axilla. The acorns are also bristled like echini, with this scaly prolongation. The timber is tough and clean, resembling the white American, and suitable for staves. The stem and branches are generally very straight, as the terminal bud seldom fails, and the growing proceeds steadily, without much autumnal shoot. {35}

As oaks run more hazard in transplanting than most other kinds of trees, the greater care is necessary in procuring well-rooted, short, vigorous plants; in having the soil free of stagnating water, in timing and executing the work in a proper manner, and in hoeing around the plant, keeping the ground clean and friable on the surface during the first two or three seasons. As young oaks grow much more vigorously under considerable closeness and shelter, and as the plants are expensive, it is proper to plant, along with them, a mixture of cheaper plants, larches or other pines, which also sooner come to be of a little value, to be removed gradually as the young wood thickens up. In bleak exposed situations, it is well to plant the ground first with pines, and when these attain a height of 6 or 8 feet, to cut out a number, not in lines, but irregularly, and plant the oaks in their stead, gradually pruning and thinning away the remaining firs as the oaks rise. In general, pitting is preferable to slitting; but when the plants are very small, and the ground wet-bottomed (with close subsoil), liable to become honeycomby with frost, slitting secures the plant better from being thrown out.

Oak is by far the best adapted tree for hedge-row, or for being grown by the sides of arable fields, both {36} with respect to its own qualities, and to the growth of the adjacent crops or hedge. The bark is much thicker, and more valuable in proportion to its bulk here, than in close forest, and the timber more crooked, which is desiderated in oak, but which unfits most other trees for much else than firewood. The oak is, besides, as generally suited for the variety of soils which lines crossing a country in all directions must embrace: this is matter of consideration, as few planters have skill to locate a number of kinds properly. It will also be thought, by reason of British feeling, the most interesting and ornamental; nor is it to be overlooked, that, by the roots taking a more downward direction than other trees, the plough has greater liberty to proceed around, and the moisture and pabulum necessary to evaporation and growth are not drawn from the ground so superficially; thence the minor plants adjacent do not suffer so much. We have observed, too, that, when all cause of injury by root suction was cut off by a deep ditch, the undergrowth seemed less injured by shade of oak than of some other trees. The apple and the pear only, appear to be as little detrimental to the surrounding crop as the oak. The ash, the elm, the beech, in Scotland the most general hedge-row trees, are the most improperly located; the ash and the {37} elm as being the most pernicious to the crops, and the beech as being of little or no value grown in hedge-row. In clays, most kinds of trees, particularly those whose roots spread superficially, are more detrimental to the crop around than in the more friable earths, owing to the roots in clays foraging at less depth, and to the clay being a worse conductor of moisture than other earths. The disadvantages attending the planting of hedge-row with oaks are, that their removal is not in general so successful as that of other trees, especially to this exposed dry situation, and that the progress of the plant, for a number of years, is but slow; and thus for a longer time liable to injury from cattle. Fair success may, however, be commanded, by previously preparing the roots, should the plants be of good size; transplanting them when the ground is neither too moist nor too dry, and in autumn, as soon as the leaves have dropped or become brown, particularly in dry ground; performing the operation with the utmost care not to fracture the roots, and to retain a considerable ball; opening pits of considerable size for their reception, much deeper than the roots, and should a little water lurk in the bottom of the pit, it will be highly beneficial, provided none stagnate so high as the roots; firming the earth well around the roots {38} after it is carefully shaken in among the fibres; and, especially, keeping the surface of the ground, within four feet of the plant, friable and free from weeds, by repeated hoeings during the first two or three summers. Of course, if you suffer the plant to waver with the wind, or to be rubbed and bruised by cattle, or by the appendages of the plough, it is folly to expect success. On this account, stout plants, from 8 to 12 feet high, the branches more out of the way of injury, may, in sheltered situations, under careful management, be the most proper size. Much also depends on procuring sturdy plants from exposed situations. We have experienced better success with hardy plants from the exposed side of a hill, having unfibred carrot roots much injured by removal, than with others from a sheltered morass, having the most numerously fibred, well extricated roots. In cases, where, from the moistness and coldness of the ground in early summer, there was a torpor of root suction, and, in consequence, the developing leaves withering up under an arid atmosphere, we have attempted to stimulate the root action by application of warm water, covering up the surface of the ground with dry litter to confine the heat; we have also endeavoured to encourage the root action by increasing the temperature of cold light-coloured soils, by strewing soot {39} on the surface for a yard or two around the plant, and by nearly covering a like distance by pieces of black trap rock, from three to six inches in diameter. The success from the pieces of trap appeared greatest; they diminished the evaporation from the ground, thence less loss of heat and of necessary moisture; and being at once very receptive of radiant caloric, and a good conductor, they quickly raised the temperature of the soil in the first half of the summer, when bodies, from the increasing power of the sun, are receiving much more heat by radiation than they are giving out by radiation.

The oak should never be pruned severely, and this rule should be particularly observed when the tree is young. We have known several of the most intelligent gardener-foresters in Scotland err greatly in this; and, by exclusively pruning the oak plants, from misdirected care, throw them far behind the other kinds of timber with which they were mixed in planting. There is no other broad-leaved tree which we have seen suffer so much injury in its growth, by severe pruning, as the oak. The cause of this may be something of nervous susceptibility, or connected life, all the parts participating when one is injured; it may be owing to the tendency to putrescency of the sap-wood, or rather of the sap, the part around the section often decaying, especially {40} when the plant is not vigorous; or it may arise from some torpor or restricted connection of the roots, which, when robbed of their affiliated branch, do not readily forage or give their foraging to the support of the nearest remaining branch, or to the general top of the tree, but throw out a brush of twigs near the section.

Although the oak often lingers in the growth while young, yet, after it attains to six inches or a foot in diameter, its progress is generally faster than most other kinds of hard wood, not appearing to suffer so much as others from excessive fruit-bearing. The value of the timber, and also of the bark, and the slight comparative injury occasioned to the under crop, whether of copse, grass, corn, or roots, independently of any patriotic motives, or religious reverence lingering in our sensorium from the time of the Druids, should give a preference to this tree for planting, wherever the soil and climate are suitable, over every other kind, with the exception of larch and willow, which, in particular soils, will pay better.

The planter of oak should throw in a considerable proportion of Turkish oak into the more favourable soils and situations. The beautiful clustered, fretted foliage of this species gives a richness, and, in winter, when it retains the withered leaf, a warmth of colouring to our young plantations beyond any other {41} of our hardy trees and shrubs. We have had this kind, eighteen years old, equal in size to larches of the same age in the same ground. We cut down several of these oaks of about 8 inches in diameter, and compared the timber and bark with those of common oak of the same age. The timber was clean, very tough and flexible, with much flash, and we should suppose might suit for plank when matured; at any rate, from the splendid shew of the laminæ (flash), it would form beautiful pannelling and furniture. It shrunk, however, extremely while drying, which must have been partly owing to the quick growing and youngness, it thence consisting almost entirely of sap-wood, and this sap-wood almost entirely of sap; and, when left in the sun in the round state, after peeling, rent nearly to splinters—much more than the common oak under the same exposure. The bark was about double the thickness and weight of that of the common oak of equal size, and, in proportion to its weight, consisted much more of that cellular or granular substance most productive of tannin. The varieties of common oak with thick bark are generally of inferior quality of timber; but they are by far the finest, most luxuriant growing trees, with rich heavy foliage, and appear as giants standing in the same row with {42} the thin barked varieties, though planted at the same time.

To the naturalist the oak is an object of peculiar interest, from the curious phenomena connected with the economy of numerous insects who depend upon it for existence. It would be tedious to describe the different apples, galls, excrescences, tufts, and other monstrosities which appear upon the oak. It is something like enchantment! These insects, merely by a puncture and the deposition of an egg, or drop of fluid, turning Nature from her law, and compelling the Genius of the Oak to construct of living organized oak matter, instead of leaves and twigs, fairy domes and temples, in which their embryo young may lie for a time enshrined.